Explosion-proof lighting fixture having isolated compartments



Nov. 13, 1951 T. E. MCDOWELL ETAL 2,574,882

EXPLOSION-PROOF LIGHTING FIXTURE HAVING ISOLATED COMPARTMENT Filed Jan. 13, 1949 mmv f M www l l l@ M EMME. www 5W@ nw? www, I 4/ Patented Nov. 13, 1951 EXPLOSION-PROOF LIGHTING FIXTURE HAVING ISOLATED COMPARTMENTS Thomas E. McDowell and Philip S. Rockwell, Chicago, Ill., assignors to The Pyle-National Company, Chicago, Ill., a corporation of Illinois Application January 13, 1949, Serial No. 70,624

6 Claims.

" r called explosion-proof lighting xtures have been provided heretofore which are adapted to provide an incandescent source of light suitably encased so as to reduce the hazards due to the inadvertent transmittal of a iiame or spark capable of igniting the explosive mixtures surrounding such a lighting xture.

The problems confronted by manufacturers of explosion-proof lighting xtures are manifold inasmuch as it is necessary to conform to a high standard of perfection established by the Underwriters Laboratories in the face of increased costs of production.

It is an object of this invention to provide an explosion-proof lighting fixture with improved serviceability characteristics and which is completely reliable for its intended purpose.

It is an object of this invention to provide an explosion-proof lighting fixture having a removable wiring canopy which has an especially designed eXplosion-proof slip joint on one end cooperatively engageable with the lamp housing.

It is a further object of this invention to provide an explosion-proof lighting fixture having a simpliiied construction whereby replacement of a lamp bulb may be accomplished without necessitating the removal of the lamp reflector.

Another object of this invention is to provide an explosion-proof lighting xture which may be conveniently serviced in the field.

A further object of this invention is to provide a wiring canopy for an explosion-proof lighting fixture having novel means of accommodating a conductor wire to be connected to a terminal block mounted in the wiring canopy and connected to a lamp accessory.

Another object of the invention is to provide an improved enclosure unit as well as improved mounting means therefor whereby the enclosure unit may be removably mounted on a fixture housing.

Yet another object of this invention is to provide a specially designed wiring canopy capable of receiving in resilient assembly .therewith a shock-absorbing mount for a lamp receptacle.

Other advantages and objects of the present invention will be manifested to those skilled in the art through reference to the following description and the accompanying drawings which describe and illustrate an explosion-proof lighting iixture embodying the principles of this invention.

On the drawings:

Figure 1 is an elevational view partly broken away and partly in section of an explosion-proof lighting fixture embodying the principles of our invention;

Figure 2 is a sectionalized fragmentary View of a portion of the wiring canopy embodied in the present structure magnified to illustrate the details of construction of the same;

Figure 3 is a fragmentary magnified sectionalized view of a portion of the wiring canopy shown in Figure 2 illustrating one modication of the present invention;

Figure 4 is a perspective view of an especially designed resilient mount embodied in the present structure; and

Figure 5 is an enlarged fragmentary sectionalized view showing an alternative modification of a portion of the structure.

As shown on the drawings:

Referring to Figure 1, an explosion-proof lighting fixture is indicated generally at I0 and comprises an enclosure unit which may include an outer reector II, a guard I2 and a globe I3; an inner reflector I4, a bulb I5, a housing I6 and a wiring canopy I1.

As may be seen on the drawing, the housing I6 comprises a hollow substantially bell-shaped member which defines on its large end a chamber for receiving a bulb receptacle I8. The small end of the housing I 6 deiines a substantially cylindrical bore which is internally threaded as at I'a and which may be machined to form a smooth cylindrical bore, as at I6b, for reasons which will hereinafter be set forth.

The wiring canopy I1 is herein shown as an integral casting having formed on one end thereof a substantially cylindrical portion which may be received generally by the bore effected by the internal bore of the housing I6. The other end of the wiring canopy herein shown defines an enlarged cap portion I'Ia.

The enlarged cap portion Ila of the wiring canopy I'I is provided with suitable entry apertures for receiving electric conduits in assembly therewith and may also be provided with suitable connecting means fcr mounting upon a wall or ceiling surface. It will be understood,

of course, that the constructional features of the wiring canopy at the enlarged cap portion IIc may be varied, as for example, by providing a simple cover structure with a central aperture whereby the explosion-proof lighting xture may be adapted for use as a pendentunitT As shown in Figure" 1, the'v wiring canopy I'I is provided with an intermediate cylindrical portion Ilb which is externally threaded as at I'Ic. Thus, when the wiring canopy I7 is inserted into" the internal bore of the housing I6," the housing and the canopy may be joined-in threaded a's`= sembly. A set screw I9 is providedto Ylock theA wiring canopy in :firm assembly with the housing.

Interiorly of the cylindrical Jp'rtion ofA the canopy I'Ib of the canopy II vis a flattened portion I'Id. A conventional terminal block 20 made of non-conducting material is mounted/upon the liattened portion IId and is held in firm assembly Y therewith .by meansof a plurality of screws a.

YUsing the plane of reference on the drawing, the left-hand portionl of. the wiring canopy I I is shown as comprising an explosion-proof slip joint I'Ie, the outside Vsurface of the slipjoint bei-ng. machinedin the formof a smooth cylinder so as to be snugly received by the cylindrical bore portion I6b of the housing I6. The longitudinal vdimension 'of theslip` joint IIe and the 'amountof tolerance between the'ho'usingjl and the wiring canopyy I'Iat the point' Ib arecritical dimensions which must be maintained in accordance with. the specicationshprescribed bythe Underwriters Laboratories...Y Thusg. .it will be evident thatvany: ame passing through the explosion-proof slip jointV I'Iefwill be cooledv suv ciently by the timefit reaches .the'other side so as to preclude-.the possibility of igniting any gaseous vapors or explosive air mixtures. l

AsV may be seen on vthe drawings, the end of the -wiring canopy- I1 is partially closed as -at I 1f. The closure'portion'llf is provided with an enlargement as at I'Ig, the detailsof which will'inow be described. l Referring specifically tFigures A2 and 3,t-he enlargement I'Ig` may Vbe-,adapted-to receive in flame-tight relation therewithfa conductorecarrying 4plug 2l. As shown .on Figure 2, a icon- ,ductor conduit 22 is molded integrally withthe plug 2l which-is made of a moldable material such as Bakelitey or the like, and the longitudinal dimension of the internal bore dened by the conductor conduit 22 within the plugZI -is maintained in accordance with the specifications' of the Underwriters Laboratories. The .plug 2| may be assembled with the wiring canopy I' I in various ways. However, as shown herein, 'the enlargement I'Ig is d rilled and tapped and the plug 2l is threaded ,upon its outer periphery kso as to permit rm threaded lassembly of the two Ymembers. vThe plug 2I may be locked. in place by means. of `a set screw.f23. It will be understood, of course, that the plug 2|, if nonrthreaded, could be assembled in other manners, as for example, by cementing..

Referringv specically to Figure 3, a rnodied conductor Vplugd2la is shown having bushings `f24 made Vof conducting material moldedintegrally therewith. The bushings may-be suitably formed to define recesses as at 24a ffor receiving in i Ysoldered connection therewith y.the terminal` end Vof` the conductors indicated by the reference numeral 22a. It will be understood, of course, that .the Vbushings24 may alsobe threaded into the `plug.2Ia, and further thatlthe plug 2m mayibe assembled with the wiring canopy I'I either in threaded relationship as is indicated at 25, or by sealing the plug 2| a. with Glyptal or some other suitable cement as at 26.

It may be notedv that the plugs 2l, 2 Ia may be formed of any suitable plastic insulating material, for example Bakelitef and comprise in dividual articles of manufacture which can be quickly replaced in a lamp structure if need be,

Vfor example, when the conductor wires are damaged and need to be replaced.

' i Referring'again to Figure 1, the lamp receptacle I8 is shown as comprising a body portion Ia having the usual terminal connectors and is surrounded byfan integral annular ring I8?) which is provided with suitable bosses as at i812. The bosses ISc :may be suitably formed to define openings for receiving mounting screws 2l. The lamp receptacle is assembled within the light structure by turning the screws 21 into the threaded receptacle of an especially designed resilient mounting member 28.

The construction of the mounting member 23 maybe seen in greater detail in Figure 4. `The member 28 takes the shape of a ring of springy, resilient metal and is bent to form two upstanding portions indicated at 28a. A pair of receptaclemounts 29 are secured to the upstanding portions 23a of the mounting 28 and are adapted to receive the screws 21 in threaded relationship therewith. The receptacle mount 28 is further provided with a pair of apertures 28h through which suitablefasteningmeans may be passed to secure the resilient mount 28 to the wiring canopy I'I as at Il'h.

Thus, it will beevident that the bulb I5 and the bulb receptacle I 8' may be subjected to strong shock without damage becauseof the shock absorbingcharacteristics allorded by the resilient inter-relation of the lamp, the bulb receptacle I8, and the wiring canopy Il.

Referring now to the left-hand portion of Figure l, the large end of the bell-shaped housing IB is shown as providing an internally threaded bore IBc. An annular clamping ring 3Q is threadedlyreceived by the threaded bore ISc of the housing I6 and maybe locked in i'lrm assembly therewith by means of a knurledscrew 3l. The clamping ring 30 is provided with a flat shoulder portion which is adapted to receive in abutting assembly therewith the globe I3. The glass-to-metal contact provided between the globe I3 and the clamping ring 3U should preferably be within the dimensional tolerances established by the specications of the Underwriters Laboratories..

The vclamping ring 3l) receives in threaded assembly therewith a globe retaining ring 32 which is also annular in form and has an internally threaded bore. The globe retaining ring 32 cooperatively engages a corresponding shoulder portion of the globe I3, thereby restraining the globe against longitudinal displacement and urging it into Vsnug llame-tight assembly with the Aclamping ring 3l).y A cushion ring 33 is interposed between the globe retaining ring 32 and the globe I 3 and preferably takes the form of emanen may be vtightened 'upon 'the clamping ring 30. iBy recessing Athe set screws f34 into the "elche `retaining 'ring 3'2, fGlyptaL or someiother fsiiit- 'able cement, maybe placed over `the setf'screws y34 so as to lock the seal `anclconceal -fthefscrew from the view of alca'sual observer. *This cori-- ystruction safeguards against any inadvertent fdisassembly of the explosion-proof 'joint *inasmuch vas yanyone desiring to 4-re-lainp vthe 'structure Tmay `conveniently remove the -entire reflector, guard, vglobe and ring 'assembly 'from the lhousing 'IB by loosening the knurled screw'3I and disengaging the clamping ring 3B from the 3housing I'S.

Some explosion-proof lighting iixtures -are manufactured to assume proportions o'f ruinbersorne size and are somewhat unwieldy 'due to the large diameter o'i vthe'outerreflector fI-I. Thus, vwhen 'expediting the re-lamping proce-dure in "larger `size lighting fixtures, the aforedescribezl assembly of the'enclosure unit has'cer'tain'servicing disadvantages. In-order to overcome these difficulties, the present :invention may 'be `modified to provide 'a 'semi-permanently assembled outer reflector as shown in Figure'.

Referring speciiically to AFigure '5, va Imodifled clamping ring a is shown which 'has two threaded portions 4in spaced relation upon lan outer .periplrieralisur'face The clamping ring 30a is threadedly received bythe internally threaded bore of the 4housing I6 and may be locked in f place by a knurled screw 3Ia. The clamping -ring 30a is also provided lwith .a flat Shoulder portion for receiving the globe I'3 lin explosionproof assembly therewith. '.The globe I3 is retained against the clamping ring 39a by means -of a 'globe retaining ring 32a. which is Yinternally threaded for engagement with the clamping vring 30a. A v.cushion ring '33a in interposed between the globe retaining ring ,and the globe, yand the .globe retaining ring may be locked in position upon the Vclamping ring by means of a plurality of set screws 34a. in the samemanner as previously described. An additional reflector ring Y35 is shouldered against the housing I6.

As may be seen on Figure 5, the reflector ring 35 is annular in shape and is provided with a flange which may lie in abutting relationship between the inturned edge of the outer reiiector II and the outer shoulder of the housing I6. The reiiector ring 35 is further provided with a shallow annular groove suitable for receiving the inturned edge of the outer reiiector II. The ring 35 may be locked in firm assembly with the housing IB by means of one or more screws 36.

It will be evident that this construction permits re-lamping without necessitating the removal of the outer reflector II since the knurled screw Sla, may be released and the entire enclosure structure comprising the guard i2, the globe I3, the globe retaining ring 32a and the clamping ring 30a may be removed by disengaging the clamping ring 30a from the threaded bore of the housing I6.

It will be evident that we have described an improved explosion-proof lighting fixture having novel features which facilitate serviceability characteristics and which may be produced with greatly reduced expenditure of manufacturing effort. Although we have resorted to details in the description of our invention for the sake of clarity, it will of course, be understood that the present embodiment is shown way of example only and, therefore, it should be understood that we desire to be limited only by the scope of the appended claims and prior art.

'We :claim as ourinvention:

1. .In :an explosioneproof lighting .dixture -fthe irmrnrovement'. fcomprising, 4a housing .having 1a. 'bore l:formed with an annular reduced diameter portionrof predetermined widththerein, a wiring rcanopylinsaidgbore having a :smooth cylindrical sleeve portion the fsame Width .as 'said annular `portion slidably reeeivedbyrsaid :annular portion l:and fforming together therewith Lan explosionl'proof ioint'fto isolate 'opposite Fends of saidhousing, and an externally threadedfconductor :plug having :conductor means integrally Yimbedded therein :and :extending from end to -end thereof, said cylindrical sleeve portion ofsaid wiringcanopy having fanaxially .extending ithreaded 4aper- A'ture freceiving saidfconduc'tor plug `in flame-proof "assembly iand establishing Ielectrical communica,-

tionbetweenoppositefends o'f v'said housing.

i2. In fan 'explosion-proof "lighting "fixture, fthe improvementvcomprising, anopen-'ended housing having a reduced fdiameter -annular portion -'of ypredetermined width formed therein fand having threaded portions adjacent opposite 'open ends thereof, a wiring canpoy-having .a threaded cap portion and y"a smooth cylindrical slip Vjoint por- `tion axilally spaced apart from-'one another, said slip ljoint lportion'being of substantially ythe same width as said annular portion, said canopy yhaving `said threaded -cap Aportion threadedly engageablein-one-end of said housing and forming thereby a name-proof Y-joint,fsaid `slip joint portion axially spaced apart vfrom one -ano'then'said capony having an axially extending threaded therewith a dame-tight joint, Aa V'closure 'means thre'ade'dly rengaged in the :other `end `of Asaid housing to form 4a flame-'tight ljoint and thereby to vcomplete'the isolation ofthe opposite ends vof said housing, and an externally vthreaded conductor plug having oonrluctor means integrally imbedded therein 'and extending tfrom' end Ato -end thereof, said slip ljoint portion of said wiring canopy having an -axilally extending "threaded aperture 'therein receiving'said conductor plug in flame-tight assembly to 'establish "electrical communication between opposite ends of said housing.

3. In an explosion-proof lighting fixture, a housing having a bore open at one end formed therein and a threaded portion adjacent the open end of said bore, an externally threaded clamping ring having a portion thereof threaded into said threaded portion of said bore and having a radially inwardly extending shoulder on the end thereof, a globe having 'an annular portion adapted to abut said shoulder in flame-tight assembly, and an internally threaded globe retaining ring threaded on said clamping ring to retain said globe in assembly with said clamping ring, said threaded-together portions of said housing, said clamping ring, and said globe retaining ring further constituting a dame-proof joint to complete the isolation of said bore of said housing, said clamping ring together with said globe and said globe retaining ring being removable from said housing as an integral sub-assembly.

4. In an explosion-proof lighting fixture, a housing having a bore open at one end formed therein and a threaded portion adjacent the open end of said bore, an externally threaded clamping ring having a portion thereof threaded into said threaded portion of said bore yand having a radially inwardly extending shoulder on the end thereof, a globe having an annular portion adapted to abut said shoulder in flame-proof assembly, and an internally threaded globe-retaining ring envases threaded on said clampingV` ring to retain said fglobe in assemblywith saidv clamping ring, and .to abut against the end ofsaid housing in flush assembly therewith, said threaded-together porztions of said housing, said clamping ring and said rglobe retaining ring further constituting 'a fname-proof joint to complete the yisolation of said bore of said housing, said clamping ring to- -gethergwith said globe and said globe retaining ring being removable from said housing as an :integral sub-assembly.

5. In 'an explosion-proof lighting fixture, a Ahousing having a bore-open at one end formed .therein'and a threaded portion adjacent the open Vend of said bore, an externally threaded clamp- Ting ring having a portion thereof threaded into said'threaded portion of said bore, and having a radially inwardly extending shoulder on the l-end.thereof, a globe having an annular portion Vadapted to,v abut said shoulder in name-proof ',assembly, an internally threaded globe retaining 1ring threaded onsaid clamping ring to retain said globe in assembly with said clamping ring andv to 'abut against the end of said housing in -flush assembly therewith, said threaded-together 'portions of said housing, said clamping ringand said globeretaining ring further constituting a Aflame-proof joint to complete the isolation of said `bore of said housing, a reflector and a globe guard gmounted on said globe retaining ring, said clamp- Aing ring 'together with said globe retaining ring, said globe, said reflector and said globe guard Ybeing removable from said housing as an integral sub-assembly.

Vvt5. An explosion-proof lighting fixture compris- -ing an open ended housing having -a reduced di- 'ameter annular rib vformed therein and having threaded Vporti-ons adjacent the .opposite ends thereoil said annular rib being of a predetermined width, awiring canopy having a threaded cap -portion and-a smooth cylindrical slip joint portion axially spaced apart from one another, said canopy having said threaded cap portion threadedly engaged in one end of said housing to form ,a flame-tight joint and having said slip joint Vend of said bore, said clamping ring having a radially extending shoulder on the end thereof, a globe having an annular portion adapted to abut said'shoulder in name-proof assembly and an internally threaded globe retaining ring threaded on said yclamping ring to retain said globe in assembly with said clamping ring, said threaded-together portions of said other end of said housing, said clamping ring and said globe retaining ring constituting a flame-proof joint to complete the explosion-proong of said housing, said clamping ring together with said globe and said globe retaining ring being removable fromsaid housing as an integral sub-assembly. THOMAS E. McDo-WELL.

PHILIP S. ROCKWELL.

'REFERENCES CITED The following references are of record in the file of this patent:`

i STATES PATENTS Number Name Date 1,730,836 Wyman Oct. 8, 1929 1,821,406 Sawin Sept. 1, 1931 2,094,394 Bissell v Sept. 28, 1937 2,278,974 Christensen v Apr. 7, 1942 j 2,316,835 Blood r Apr. 20, 1943 2,339,670 Benson Jan. 18, 1944 2,422,379

Westman June 17, 1947 Certificate of Correction Patent N o. 2,574,882 November 13, 1951 THOMAS E. MCDOWELL ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 38, for in interposed read is interposed; column 6, line 24, for canpoy read canopy; lines 26 and 3, for axilally read axially; lines 32 and 33, for axially spaced apart from one another, said ca ny having an axially extending threaded read being concurrently received??? said annular portion in slz'dable relation to form, together;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Olce. Signed and sealed this 4th day of March, A. D. 1952.

THOMAS F. MURPHY, Assistant Gommzm'oner ofPfenh. 

